Compiler segfaults when boxing a ZST from an external crate #28766
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I-ICE
Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️
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Looks like this is tripping an LLVM assertion: I think if you use nightly it's got LLVM assertions enabled, which is why it looks like a segfault on stable! |
alexcrichton
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backtrace? |
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cc @dotdash |
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Backtrace for me looks like: |
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Problematic IR: Why is there a and compiles on vanilla and rustc |
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cc @dotdash |
It looks like a real LLVM bug, but one that rustc could easily dodge by generating |
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Quoting the LLVM reference:
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Closed
dotdash
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Jan 15, 2016
The only way to get a value for a zero-sized type is `undef`, so there's really no point in actually having a return type other than void for such types. Also, while the comment in return_type_is_void mentioned something about aiding C ABI support, @eddyb correctly pointed out on IRC that there is no such thing as a zero-sized type in C. And even with clang, which allows empty structs, those get translated as void return types as well. Fixes rust-lang#28766
Manishearth
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Jan 17, 2016
The only way to get a value for a zero-sized type is `undef`, so there's really no point in actually having a return type other than void for such types. Also, while the comment in return_type_is_void mentioned something about aiding C ABI support, @eddyb correctly pointed out on IRC that there is no such thing as a zero-sized type in C. And even with clang, which allows empty structs, those get translated as void return types as well. Fixes rust-lang#28766
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Demonstration
I uploaded a repo with the simplest possible case I could come up with that demonstrates this issue here. Here's how it works:
$ rustc --version --verbose rustc 1.4.0-dev (d2e13e822 2015-09-15) binary: rustc commit-hash: d2e13e822a73e0ea46ae9e21afdd3155fc997f6d commit-date: 2015-09-15 host: x86_64-apple-darwin release: 1.4.0-dev $ git clone https://github.com/kylewlacy/rust-segfault.git $ cd rust-segfault $ cargo build --release --verbose Compiling my_crate v0.1.0 (file:///Users/kyle/Desktop/rust-segfault) Running `rustc my_crate/src/lib.rs --crate-name my_crate --crate-type lib -C opt-level=3 -C metadata=ab97f46dd8433ebe -C extra-filename=-ab97f46dd8433ebe --out-dir /Users/kyle/Desktop/rust-segfault/target/release/deps --emit=dep-info,link -L dependency=/Users/kyle/Desktop/rust-segfault/target/release/deps -L dependency=/Users/kyle/Desktop/rust-segfault/target/release/deps` Compiling segfault v0.1.0 (file:///Users/kyle/Desktop/rust-segfault) Running `rustc src/lib.rs --crate-name segfault --crate-type lib -C opt-level=3 --out-dir /Users/kyle/Desktop/rust-segfault/target/release --emit=dep-info,link -L dependency=/Users/kyle/Desktop/rust-segfault/target/release -L dependency=/Users/kyle/Desktop/rust-segfault/target/release/deps --extern my_crate=/Users/kyle/Desktop/rust-segfault/target/release/deps/libmy_crate-ab97f46dd8433ebe.rlib` Could not compile `segfault`. Caused by: Process didn't exit successfully: `rustc src/lib.rs --crate-name segfault --crate-type lib -C opt-level=3 --out-dir /Users/kyle/Desktop/rust-segfault/target/release --emit=dep-info,link -L dependency=/Users/kyle/Desktop/rust-segfault/target/release -L dependency=/Users/kyle/Desktop/rust-segfault/target/release/deps --extern my_crate=/Users/kyle/Desktop/rust-segfault/target/release/deps/libmy_crate-ab97f46dd8433ebe.rlib` (signal: 11)Explanation
So I have a crate in my project, brilliantly named
my_crate.my_crateis pretty simple, it contains a struct, calledFoo, made up of zero-sized types.Fooalso has a constructor function calledFoo::new():Now, in my library,
segfault, I have a single function, calledbox_foo(), that just returns aBox<Foo>. It constructs aFoo, then boxes it:Well, that's about it. Building
segfaultandmy_cratewithcargo buildworks perfectly fine. However,cargo build --releasecrashes with a signal 11, a segfault.Some observations
Foomust be a zero-sized type, but cannot be a unit structFoomust be constructed with a function (e.gBox::new(Foo(())would not segfault)Foomust be from another cratebox_foo()is public (otherwise it's dead code, and I guessrustcdoesn't even attempt to compile it?)impl Foo, but it does have to come frommy_cratelet boxed: Box<Foo> = Foo::new_box();would not segfault)Foohas the same issueBox<Foo>, but by constructing one withBox::new. That is, the following also causes a segfault:The text was updated successfully, but these errors were encountered: